Shell script hangs on mail command

Question

I'm finding that a call to the mail command is causing a script to suspend without error. To close the script I have to ctrl-c or issue a kill command on the process id.

The pertinent section of the script is below:

EMAIL_TO="my@email.com"

if [ -f /www/archives/pdf/pdf_201207021048.tar ]; then
    echo "file exists"
else
    echo "file does not exist"
fi

echo "sending mail next..."

mail -s "pdfbackup" "$EMAIL_TO"

echo "mail sent?"

When running this, I'm seeing the text "sending mail next..." and nothing more. It never returns to prompt.

I can see the script is still in memory with ps -ax | grep myscript.sh.

I've tried using quotes around the subject and email, and again without. The same result is produced either way.

What am I doing wrong?

also asked on stackoverflow: http://stackoverflow.com/q/11298463/7552 — glenn jackman, Jul 02 '12 at 20:09
@glennjackman - is there a preference for posting shell scripting questions? I see more of it on SO, though they could also go here. — a coder, Jul 02 '12 at 20:27
@acoder You can post on either (unix shell scripting is on-topic both on SO and here), but not both. — Gilles 'SO- stop being evil', Jul 02 '12 at 21:58

score 15 · Accepted Answer · answered Jul 02 '12 at 17:50

The mail program expects the user to type the message on its standard input (terminated by EOF (Ctrl-D)). You are not redirecting stdin, the program is waiting for input. You can either redirect from /dev/null (for an empty message), from a canned file, or from a pipe, for example:

echo Hi, just sending you a message | mail -s "pdfbackup" "$EMAIL_TO"

or

mail -s "pdfbackup" "$EMAIL_TO" < /dev/null

Both of these should clear up problem.

Shell script hangs on mail command

1 Answers1

Linked